Antirollback mechanism



United States Patent [72] Inventor David H. Seaberg Burlington, Iowa [2]] Appl. No. 762,724 [22] Filed Sept. 26, 1968 [45} Patented Nov. 10, 1970 [73] Assignee J.I. Case Company a corporation of Wisconsin [54] ANTIROLLBACK MECHANISM 6 Claims, 7 Drawing Figs.

[52] US. Cl 214/764 (51] Int. Cl E02f 3/28 [50] Field of Search 214/762, 763, 764, 773, 775, 776

[56] References Cited UNITED STATES PATENTS 3,402,840 9/1968 Goth 214/764 3,432,057 3/l969 Goth 214/764 Primary Examiner-Hugo O. Schulz AttorneyDressler, Goldsmith, Clement & Gordon ABSTRACT: A loader unit mounted on a tractor and including pivotally mounted lift arms pivotally carrying a bucket and all controlled by a hydraulic circuit, including a lift arm control cylinder and a bucket control cylinder. The hydraulic control circuit incorporates a lift arm control valve spool and a bucket control valve spool operable by a single control lever. The loader unit also includes a mechanical return to dig linkage having a latch engageable with the single control lever to hold the lever in bucket rollback position as the arm is lowered. An adjustable linkage connected to the latch prevents operation of the bucket control valve spool to roll the bucket rearwardly past its level position when the lift arms are in raised position, thereby preventing rearward dumping of the bucket.

Patented Nov. 10, 1970 3,539,068

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Sheet 3 of 3 //V VENTOQ .DZOZZZ deafie QTTOP/Vf/S ANTIROLLBACK MECHANISM BACKGROUND OF THE INVENTION Material handling devices, such as loaders mounted upon and controlled byv various vehicles, are well known. Such loaders include lift arms pivotally mounted to the vehicle, which lift arms carry a pivotally mounted bucket at their free end. A hydraulic lift cylinder is connected between the vehicle or support thereon and each lift arm to raise and lower the lift arms, and at least one bucket hydraulic cylinder is connected between the lift arms and the bucket to position the bucket relative to the lift arms.

A slave cylinder is provided to modify the action of the bucket cylinder in accordance with swinging movement of the lift arms for maintaining the bucket in a substantially level position. A typical self-leveling arrangement of this type is shown in Long U.S. Pat. No. 3,220,580.

Such arrangements are subject to rearward dumping of the bucket in the event of operator error. When the lift arms are raised, such rearward dumping of the bucket may present a substantial danger to the operator. While various hydraulic systems have been designed for incorporation into different types of material-handling devices, such systems are not suitahle for loaders which are currently in use. Thus, there is a requirement and a serious need for some modification which can be made to existing material-handling devices to introduce the necessary safety factor and prevent the possibility that the bucket might inadvertently be actuated in a fashion to cause rearward dumping when the lift arms are raised.

SUMMARY OF THE INVENTION The present invention is directed to a positive, adjustable, antirollback mechanism which cooperates with mechanical return to dig linkages in material handling devices incorporating a single control lever for operating both the lift arms and the bucket. In such a configuration, a typical mechanical return to dig linkage is provided and coupled between the bucket at one end and a return to dig latch at the other.

The operation of the linkage is governed both by the position of the bucket relative to the lift arms and of the position of the lift-arms. When the lift arms are raised and the bucket has been dumped. the return to dig latch is in position to hold the control lever when moved into a float and rollback position until the lift arms have generally lowered and the bucket rolled back.

When the position of the bucket relative to the lowered lift arms is such that the bucket will be in digging position when the lift arms are completely lowered, the return to dig latch automatically moves forward and releases the control lever allowing it to return to a neutral position relative to its bucket control function, while allowing the lift arms to gradually settle into digging position under their own weight.

While it is desirable to automatically roll back the bucket under these conditions, it is undesirable to be able to roll the bucket back beyond a level position when the lift arms are raised, since this would allow a load to be inadvertently dumped on the machine and, if the arms are high enough, onto the operator.

As explained above, the return to dig linkage and latch releases the control lever as the bucket rolls back from a dump position into a dig position relative to the arms. This relationship can be utilized to prevent additional rollback of the bucket beyond its desired limit. Such antirollback mechanism can be incorporated as an additional mechanical linkage connected to the return to dig latch. This antirollback linkage provides an adjustable but positive means designed to engage a stop coupled to the bucket control valve spool to prevent its actuation when the bucket has rolled back to a level position while the lift arms are raised.

Such an antirollback mechanism should be readily installable on existing material-handling devices, should be easily installable while the loader is in the field and should not require substantial alterations of existing parts or extensive modifica tion or rearrangement of such parts. It is also desirable that such an antirollbaek mechanism, while providing a positive stop against rearward dumping of the bucket, should be adjustable to allow for variations in each apparatus due to the normal wear and tear and also to allow for the varying uses to which such material-handling devices are put.

Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and of one embodiment thereof, from the claims and from the accompanying drawings in which each and every detail shown is fully and completely disclosed as part of this specification, in which like reference numerals refer to like parts, and in which:

FIG. 1 is a side elevation of the loader mechanism, showing in solid lines the bucket in the digging position and in dotted lines the bucket in lifting position;

FIG. 2 is a side view similar to FIG. I, showing in solid lines the lift arm and bucket in fully raised position and in dotted lines the positions of the various components after the bucket has been dumped;

FIG. 3 is a plan view of the untirollbnck mechanism and the control lever.

FIG. 4 is aside view ofthe antirollbnck mechanism;

FIG. 5 is a partial sectional view taken along lines 5-5 of FIG. 3;

FIG. 6 is a perspective view showing operation of the return to dig latch; and 2 FIG. 7 is a diagrammatic plan view of the antirollback linkage.

Referring now to FIGS. 1 and 2, there is shown a materialhandling device which includes a loader mechanism 12 mounted on a front end of a tractor 14. The loader mechanism 12 includes a main frame 16 that is attached to the tractor [4 by any suitable means. The main frame 16 serves as the main support member for the loader mechanism 12 and includes a pair of uprights 18 (only one being shown) spaced on opposite sides of the tractor 14 connected at their upper ends by a pivot shaft 20. Although only one side of the loader mechanism is shown, it should be understood that the various components are normally present on both sides ofthe tractor Id.

The loader mechanism 12 consists of a pair of lift arms 22 pivotally connected to the upper end of the uprights 18 by the pivot shaft 20. A bucket 24 is pivotally connected to the forward cnd ofthc lift arms 22.

Each lift arm 22 is pivoted about the pivot shaft 20 by operation of a hydraulic cylinder 26 through the extension or retraction of a piston rod 28 extending outwardly from the cylinder 26. The lower end of each lift arm cylinder 26 is pivotally connected to the lower portion of an upright 18. while the outer end of each lift arm cylinder piston rod 2% is pivotally secured to an intermediate portion of one lift arm 22.

When hydraulic pressure is applied to the piston end of the hydraulic lift arm cylinders 26, the lift arms 22 are raised by pivoting about the pivot shaft 20. Conversely, when pressure is applied to the rod end of lift arm hydraulic cylinders 26, the lift arms 22 are pivoted in an opposite direction to lower the bucket 24 attached to the end of the arms.

The bucket 24 is pivoted relative to the lift arms 22 between carrying and unloading positions by at least one hydraulic bucket cylinder 30. The piston rod 32 of the bucket cylinder 30 is connected to the lift arms 22 near the end thereof, while the cylinder 30 itself is coupled to the bucket 24 through a bucket-positioning linkage 34.

The bucket-positioning linkage 34 includes .a forward bucket link 36, one end of which is pivotally secured to the bucket 24 and the opposite end of which is pivotally connected to the end of a rear bucket link 38. The opposite end of the rear bucket link 38 is pivotally connected to an intermediate portion of the lift arms 22. It can thus be seen that pivotal movement of the rear bucket link 38 causes pivotal movement of the bucket 24 relative to the lift arms 22. To effectuate movement of the rear bucket link 38, the bucket hydraulic cylinder 30 is pivotally connected thereto intermediate its ends.

Application of hydraulic pressure to the rod end of the bucket cylinder 30 causes the bucket 24 to pivot forwardly relative to the lift arms 22. Conversely, application of hydraulic pressure to the piston end of the bucket cylinder 30 causes the bucket 24 to pivot rearwardly.

It can be appreciated that when the lift arms 22 are raised, the bucket 24, if it remains in a fixed position relative to the arms 22, tends to tilt rearwardly. As a result, a load in the bucket 24 would be dumped back onto the tractor l4 and onto the operator. A slave cylinder 40 connected between the lower region of the upright 18 and the rear end of one lift arm 22 provides self-leveling of the bucket 24 as the lift arms 22 are raised. The leveling action of the present arrangement is functionally similar to that shown in H6. 2 of Long US. Pat. No. 3,220,580 with the exception that operation of the lift arms 22 and bucket 24 in the present arrangement is effected through a single control lever as will be explained below.

However, in the arrangement of Long U.S. Pat. No. 3,220,580, control of the hydraulic bucket cylinder may be effected independently of the position of the lift arms so that the bucket cylinder can be operated fully in either direction when the arms are raised. in the event of operator error, this allows the bucket to be tilted rearwardly thereby dumping a load back on the vehicle. This can be quite dangerous to the operator, particularly when large loads are being handled.

in accordance with the present invention, there is provided a mechanical interlock effective when the lift arms 22 are raised above a selectable position to prevent rearward tilting of the bucket 24 past its level position while permitting forward tilting ofthe bucket 24 for dumping of the load. Thisantirollback interlock operates in conjunction with a mechanical return to dig linkage 44 which operates to return the bucket 24 to digging position from dump position when the lift arms 22 are lowered.

As can be appreciated, when the bucket 24.is dumped, the bucket must be rolled back in order that it achieve a dig position, shown in solid lines FIG. 1, when the lift arms 22 are lowered to position the/bucket 24 at ground level. One such return to dig linkage 44 is specifically designed in cooperation with single control lever 46, operation of the lift arms 22 and buckethydraulic cylinder 30. Such a control lever 46, as shown in FIGS. 3, 4 and 6, enables an operator to actuate the lift arm hydraulic cylinder 26 and/or the bucket hydraulic cylinder 30 by moving the single control lever 46. Movement of the control lever 46 actuates two adjacent spools 47, 48 of a hydraulic control valve, each respectively controlling operation of the lift arm and bucket control cylinders 26, 30, respectively.

For example, movement of the control lever 46 longitudinally of the tractor 14 on which it is mounted, actuates only the lift arm spool 47, while transverse movement of the control lever 46 actuates only the spool 48 controlling the hydraulic bucket cylinder 30. Combined longitudinal and transverse movement will actuate both spools 47,48.

Pulling the control lever 46 to the rear operates the lift arm spool 47 to raise the lift arms 22, moving the control lever 46 forward operates the spool to lower the lift arms 22 and pushing the control lever 46 all the way forward into a detent float position allows the lift arms 22 to lower under their own weight. In the illustrated embodiment, transverse movement of the control lever 46 to the left rolls back the bucket 24 relative to the lift arms 22, while transverse movement of the control lever to the right tilts the bucket 24 forward.

The bucket movement results from the arrangement of the pivotal connections between the control lever 46 and lift arm and bucket control valve spools 47, 48. The lower end of the control lever 46 is transversely pivotally mounted in a pivot block 49. The pivot block 49 is rotatably supported on a transverse pin 50 (FIG. 4) thereby allowing longitudinal movement of the control lever 46. A lug 52 provided on the top of the pivot block 49 is connected to the lift arm control spool 47, and therefore when the control lever 46 is moved longitudinally, the lift arm control spool 47 is operated.

The control lever 46 is also provided with a laterally extending L-shape extension 54 which terminates in a lower ball joint 56 which is suitably located to remain stationary when the control lever 46 is moved longitudinally. Since the lower ball joint 56 is located to one side of the pivot block 49, it is raised and lowered during transverse movement of the control lever 46. The lower ball joint 56 is connected through a vertical bucket control link 58 and a transverse bucket control link 60 to the bucket control spool 48. Thus, when the lower ball joint 56 is raised and lowered during transverse movement of the control lever 46, the transverse bucket control link 60 is rotated, thereby operating the bucket control spool 48 to cause rearward and forward tilting of the bucket 24.

The rotational movement of the transverse bucket control link 60 during transverse movement of the-control lever 46 is utilized to prevent bucket rollback in conjunction with automatic return ofthe bucket 24 to dig position as the lift arms 22 are lowered. The mechanical linkage 44 connected to the rear bucket link 38 is utilized to effect this return to dig function.

This linkage 44consists of a push rod 62 having a telescoping portion 64 at one end connected to the rear bucket link 38. The other end of the push rod 62 is connected to an intermediate link 66 pivotally supported on the upright l8."l'he other end of intermediate link 66 is connected to a horizontal extension 68 which terminates in a pivotal connection with a return to dig latch 70. One end of the return to dig latch 70 is pivotally supported adjacent the control lever 46 and the other end is free to move longitudinally of the tractor 14 in response to movement of the linkage 44.

When the bucket 24 is dumped, the push rod 62 is pulled forward, thereby moving the return to dig latch 70 renrwardly into a control lever-holding position (FIG. 6). When the control lever 46 is pushed forward into the float position, where it is held by a valve detent (not shown), and to the left into the bucket rollback position, it is held to the left by the end of the return to dig latch 70 which engages a lug 72 on the control lever 46.

During initial rollback remains stationary since the telescoping portion 64 allows initial movement of the bucket 24 to occur without affecting the linkage 44. When the telescoping action of the push rod 62 is completed, the push rod 62 is moved rearwardly of the tractor 14 causing the horizontal extension 68 to move forwardly, pulling the return to dig latch 70 forward to release the control lever 46 from its rollback position. The control lever 46, which is suitably biased towards neutral bucket position, returns to this position but remains in its float position due to the detent lift arm valve spool 47. The geometry of the lift arm 22 and linkage 44 is designed to automatically compensate for leveling by the slave cylinder 40 during the remainder of the lowering cycle so that the bucket 24 is in dig position when the arms 22 are completely lowered.

From the above, it is clear that the position of the return to dig linkage 44 and latch 70 is controlled both by the position of the bucket 24 relative to the lift arms 22 and by the position of the lift arms. Thus, when the bucket 24 is rolled back to its level position, the return to dig latch 70 is pulled forward out of the way of the control lever 46. It is possible to utilize this relationship to prevent operation of the control lever 46 to roll back the bucket 24 past the level position while the lift arms 22 are raised.

The antirollback mechanism can be seen most clearly in FIGS. 3-7. The antirollback mechanism is incorporated in a three-bar reverse operating linkage 74 connected to the return to dig latch 70 which operates as an actuating member. The three-bar linkage 74 includes a lever 76 pivotally mounted intermediate its ends at a point forward of the return to dig latch 70. A pair of links 78, are pivotally connected to the ends of the lever 76.

The first or connecting link 78 has its other end pivotally secured to the return to dig latch 70 at the point of connection to the return to dig linkage 44. The second or stop link 80 nttachcd to the other end of the lever 76 extends renrwardly past of the bucket 24, the push rod 62,

the return to dig latch 70 to a point where the end of the stop link 80 is in position to engage a stop projection 82 formed on the transverse bucket control link 60.

It can be seen that due to the configuration of this antirollback linkage 74, the stop link 80 moves forward away from the transverse bucket control link 60 when the return to dig latch 70 is moved rearwardly into position to hold the control lever 46 in rollback position, i.e., when the bucket 24 is tilted forward. As the bucket 24 is rolled back, the return to dig latch 70 is pulled forward, as explained above, to release the control lever 46. This causes the antirollback stop link 80 to move rearwardly into its operative position.

If at this point an attempt is made to move the control lever 46 transversely into bucket rollback position, transverse bucket control link 60 rotates so the stop projection 82 on the transverse bucket control link 60 engages the end of the antirollback stop link 80, thereby preventing movement of the control lever 46 into the rollback position. if the control lever 46 is already in the transverse bucket rollback position, the end of the antirollback stop link 80 engages the stop projection 82, rotating the transverse bucket control link 60 rearwardly to force the controllever 46 into neutral.

As the lift arms 22 are lowered, and the bucket 24 is automatically returned to the dig position, the antiroliback linkage 74 retracts from its operative position to allow the bucket 24 to be rolled back into carry position after the bucket is loaded.

in order to accommodate variations in machines to allow for the different uses to which they may be put, the rollback stop link 80 is provided with a threaded portion 84 to permit adjustment of the length of the stop link 80 so it can be set to engage the stop projection 82 at various desired positions of the lift arm 22 and of the bucket 24.

Thus, there has been disclosed a mechanical, positive, adjustable mechanism for preventing rollback of a bucket in a material-handling device into a position where possibility of rearward dumping can occur, which mechanism can readily.

be added to existing apparatus having mechanical return to dig function and a single control lever for hydraulically operating both the lift arm and bucket. Such antirollback mechanism can be added without modification or replacement of existing parts and can be readily adjusted for various intended uses and for varying conditions of the apparatus to which it is attached.

it will be readily observed from the foregoing detailed description of the invention and in the illustrated embodiments thereof that numerous variations and modifications may be effected without departing from the true spirit and scope ofthe novel concepts and principles of this invention.

I claim:

I. A material-handling device comprising a support structure, lift arm means pivotally mounted on said support structure, a bucket pivotally supported on said lift arm means, a control lever, a hydrauliccircuit, means coupling said control lever to said hydraulic circuit, for raising and lowering said lift arm means and for rolling the bucket forward and back relative to said lift arm means, latch means, means connecting said latch means to said lift arm means and to said bucket for moving said latch means into engagement with said control lever when said control lever is in a bucket rollback position, when said lift arm means is raised and when said bucket is rolled forward for holding said control lever in said bucket rollback position during downward movement of said lift arm to automatically return said bucket to dig position, and an adjustable mechanical linkage, means connecting said linkage to said latch means for obstructing operation of said control lever to prevent rollback of the bucket past its level position when said lift arm means is raised in response to movement of said latch means out of engagement with said control lever.

2. A material-handling device according to claim 1 wherein said adjustable mechanical linkage includes a stop link responsive to said movement of said latch out of engagement with said control lever for preventing said bucket rollback.

3. A material-hand mg device according to claim 2 wherein said means for coupling said control lever to said hydraulic circuit includes a control link, a stop member formed on said control link and movable thereby into engagement with said stop link for preventing operation of said control lever to roll back said bucket.

4. A material-handling device according to claim 2 including means for adjusting the length of said stop link whereby said bucket is prevented from being rolled back at selected positions of said bucket and said lift arm means.

5. A bucket antirollback mechanism for a material-handling device comprising lift arm means, a bucket, a control lever, means coupling said lever to said lift arm means and to said bucket for raising and lowering said lift arm means and for rolling said bucket forward and back, a three-member adjustable linkage including a stop link, actuating lutch means, means connecting said latch means to said adjustable linkage, means for pivotally moving said latch between a first position holding said control lever in bucket rollback position and a second position releasing said control lever, and a projection positioned by said coupling means into engaging position with said stop link when said latch is in lever-releusing position to prevent movement of said control lever to roll back said bucket past level position when said lift arm means is raised.

6. An antirollback mechanism for a material-handling device comprising a support structure, lift arm means pivotally mounted on said support structure, a bucket pivotally mounted on said lift arm means, a hydraulic circuit including first and second hydraulic operating means and first and second control valves, means for connecting said first hydraulic operating means between said lift arm means and said support structure, means connecting said second hydraulic operating means between said lift arm means and said bucket, means coupling said first control valve to said first hydraulic operating means, means coupling said second control valve to said second hydraulic operating means, a single control lever, means connecting said control lever to said control valves for operating said first control valve to raise and lower said lift arm means upon movement of said control lever in a first direction,for operating said second control valve to roll said bucket forward and back relative to said lift arm means upon movement of said lever in a second direction, and for operating both of said valves upon combined movement of said lever in both said first and second directions, a first mechanical linkage, means connecting one end of said first linkage to said bucket and to said second hydraulic operating means, means pivotally connecting said first linkage intermediate its ends to said support structure, a latch pivotally supported on said support structure adjacent said control lever, means connecting said latch to said first linkage for movement under control of said first linkage between a first control lever-holding position wherein said lever is maintained in bucket rollback operating position for causing rollback of said bucket and a second control lever-releasing position, and means coupled to said linkage for interfering with said control lever when said latch is in said forward position to prevent positioning of said control lever into said 'bucket rollback operating position, a second antirollback linkage including a stop link, means connecting saidsecond linkage to said latch for moving said stop link towards said control lever-connecting means in response to said latch moving to said second control lever-releasing position, a'stop formed as a part of said control lever-connecting means and movable thereby towards said stop link in response to movement of said control lever into bucket rollback operating position whereby said stop is engaged by said stop link to obstruct operation of said control lever and prevent rollback of said bucket past its level position when said lift arm means is raised. 

